Segment CMR Reference Manual

Transcription

Segment CMR
Reference Manual
April 7, 2015
Software platform v2.0 R4265
MEDVISO AB
http://www.medviso.com
Griffelv¨agen 3
SE-224 67 Lund
Sweden
Tel: +46-76-183 6442
ii
Contents
1 Regulatory Status
1.1 Commercial usage of Segment CMR . . . . . . . . . . . . . .
1.2 Indications for use . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Investigational purposes . . . . . . . . . . . . . . . . . . . . .
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2 How to Read This Manual
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3 Conventions and Abbreviations
3.1 Typographic conventions . . . . . . . . . . . . . . . . . . . .
3.2 Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . .
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4 System Requirements
4.1 Operating system . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Hardware requirements . . . . . . . . . . . . . . . . . . . . .
4.3 Internet access . . . . . . . . . . . . . . . . . . . . . . . . . .
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5 Loading Image Stacks
5.1 Loading DICOM files . . . . . . . . . .
5.1.1 Loading DICOM files . . . . . .
5.1.2 Tips and tricks . . . . . . . . .
5.1.3 Graphical image series selection
6 Program Overview
6.1 Viewing image stacks
6.2 Montage view . . . .
6.3 Montage row view . .
6.4 One slice view . . . .
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iii
CONTENTS
6.5
6.6
6.7
6.8
6.9
Viewing velocity encoded image stacks . .
Playing images as a cine-loop . . . . . . .
Synchronizing image stacks . . . . . . . .
Loading and storing images . . . . . . . .
Tool palette . . . . . . . . . . . . . . . .
6.9.1 Left ventricle tools . . . . . . . .
6.9.2 Right ventricle tools . . . . . . .
6.9.3 Viability/Scar tools . . . . . . . .
6.9.4 Miscellaneous tool mode . . . . .
6.9.5 ROI tool mode . . . . . . . . . .
6.10 General view and reporting functionality .
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7 Measurements and Annotations
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7.1 Length measurements . . . . . . . . . . . . . . . . . . . . . . 29
8 Segmentation of the Left Ventricle
8.1 Definition of the left ventricle . . . . . . . . . . . . . . . . . .
8.1.1 Papillary muscles . . . . . . . . . . . . . . . . . . . .
8.1.2 Mitral annulus . . . . . . . . . . . . . . . . . . . . . .
8.2 Start the segmentation process . . . . . . . . . . . . . . . . .
8.3 Edit the segmentation result . . . . . . . . . . . . . . . . . .
8.3.1 Undo segmentation . . . . . . . . . . . . . . . . . . .
8.3.2 Refine segmentation . . . . . . . . . . . . . . . . . . .
8.3.3 Expand or contract segmentation . . . . . . . . . . .
8.3.4 Manually adjusting the contour by interpolation points
8.3.5 Manually drawing the contour . . . . . . . . . . . . .
8.3.6 Translating the segmentation . . . . . . . . . . . . . .
8.3.7 Scale the segmentation . . . . . . . . . . . . . . . . .
8.3.8 Manually include/exclude papillary muscles . . . . .
8.3.9 Removing segmentation result . . . . . . . . . . . . .
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9 Segmentation of the Right Ventricle
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10 Segmentation of Long Axis Images
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10.1 Click an image to show point location in all views . . . . . . 39
iv
CONTENTS
11 Regional Wall Analysis
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11.1 Radial contraction versus time . . . . . . . . . . . . . . . . . 41
11.2 Report per slice . . . . . . . . . . . . . . . . . . . . . . . . . 41
12 Flow Analysis
12.1 Automatic segmentation of flow ROI’s
12.1.1 Refine . . . . . . . . . . . . .
12.1.2 Refine and propagate . . . . .
12.1.3 Shrink flow ROI . . . . . . . .
12.2 Plotting the result of the flow analysis
12.3 Compensating for eddy current effects
12.4 Phase unwrapping . . . . . . . . . . .
12.4.1 Automated unwrapping . . . .
12.4.2 Manual unwrapping . . . . . .
12.5 Creating angio and velocity magnitude
12.6 Coupling magnitude and flow images .
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13 Bulls eye Analysis
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14 T2/T2* Quantification Module
14.1 Module overview . . . . . . . . . . . . . . . . . . . . . . . . .
14.2 Implementation . . . . . . . . . . . . . . . . . . . . . . . . .
14.3 Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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15 Strain Analysis
15.1 Velocity Encoded Imaging . . . . . . . .
15.1.1 Strain calculation . . . . . . . .
15.1.2 Corrections of the segmentation
15.1.3 Strain analysis . . . . . . . . . .
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16 Viability Analysis
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16.1 Grayzone Analysis . . . . . . . . . . . . . . . . . . . . . . . . 65
17 Myocardium at Risk Analysis
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18 Perfusion Analysis
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18.1 Module overview . . . . . . . . . . . . . . . . . . . . . . . . . 69
19 Pulse Wave Velocity Analysis
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v
CONTENTS
20 LV Sphericity Analysis
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21 Reporting
21.1 Configuration . . . . . . . . . . . .
21.1.1 Hospital logo . . . . . . .
21.1.2 Reference values . . . . . .
21.1.3 Headings for textual report
21.1.4 Reviewing doctor . . . . .
22 Export Images and Results
22.1 Export image . . . . . . .
22.2 Export screenshot . . . .
22.3 Export movies . . . . . .
22.4 Movie Recorder . . . . .
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23 Customization
23.1 Image description settings . . . .
23.2 Advanced and DICOM Settings
23.3 PACS Settings . . . . . . . . . .
23.4 Technical details . . . . . . . . .
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24 Short Commands / Hot keys
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24.1 Hot keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
25 Support
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25.1 Submit bug report . . . . . . . . . . . . . . . . . . . . . . . . 95
25.2 Data privacy policy . . . . . . . . . . . . . . . . . . . . . . . 96
25.3 General support issues . . . . . . . . . . . . . . . . . . . . . . 96
26 Implementation Details
26.1 Numeric representations . . . . . . . . . . . . . .
26.2 Loading data and interpretation of DICOM tags
26.3 Volume calculations . . . . . . . . . . . . . . . .
26.4 Mass calculations . . . . . . . . . . . . . . . . .
26.5 Calculation of BSA . . . . . . . . . . . . . . . .
26.6 Peak ejection/filling rate . . . . . . . . . . . . .
26.7 Wall thickness . . . . . . . . . . . . . . . . . . .
26.8 Calculation of regurgitant volumes and shunts . .
26.9 Infarct size, extent and transmurality . . . . . .
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CONTENTS
26.10 T2/T2* calculation implementation
26.10.1 Calculating fitting error . .
26.10.2 Smoothing . . . . . . . . . .
26.11 Longaxis volumes . . . . . . . . . .
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vii
1 Regulatory Status
1.1
Commercial usage of Segment CMR
Segment CMR bears the CE marking of conformity and is certified according to the ISO 13485 standard. Segment CMR is based almost entirely on
the software Segment which is FDA approved with FDA 510(k) number
K090833. Please note that there are features that are not included in the
FDA approval. These functions are marked in the Instructions for Use and
in the Reference Manual that they are only for investigational use. An application for FDA approval for Segment CMR is under preparation.
Users are also required to investigate the regulatory requirements pertinent
to their country or location prior to using Segment CMR. It is in the users
responsibility to obey these statues, rules and regulations.
1.2
Indications for use
Segment CMR is a software that analyzes DICOM-compliant cardiovascular
images acquired from magnetic resonance (MR) scanners. Segment CMR
specifically analyzes the function of the heart and its major vessels using
multi-slice, multi-frame and velocity encoded MR images. It provides validated and reproducible data for supporting the evaluation of the function of
the chambers of the heart such as left and right ventricular volumes, ejection
fractions, stroke volumes, peak ejection and filling rates, myocardial mass,
regional wall thickness, fractional thickening and wall motion. The ventricular analysis is provided for usage in both pediatric (from newborn) and adult
population. Segment CMR also provides quantitative data on blood flow
and velocity in the arterial vessels and at the heart valves. Quantification of
regional function is provided by fast and reproducible measuring of myocardial strain in the heart, and T2* relaxation is provided from the quantitative
T2* analysis. The data produced by Segment CMR is intended to be used
to support qualified cardiologist, radiologist or other licensed professional
healthcare practitioners for clinical decision making. It is a support tool
that provides relevant clinical data as a resource to the clinician
and is not intended to be a source of medical advice or to determine
1
CHAPTER 1. REGULATORY STATUS
or recommend a course of action or treatment for a patient.
1.3
Investigational purposes
None of the organizations/persons named in conjunction with the software
can accept any product or other liability in connection with the use of this
software for investigational purposes.
2
2 How to Read This Manual
Technical documentation always face a certain dilemma: whether write for
top-down or bottom-up learners. A top-down learner prefers to read or skim
documentation, getting a large overview of how the system works; only then
does she actually start using the software. A bottom-learner is a ’learn by
doing’ person, someone who just wants to dive into the software and figure
it out as she goes, referring to book sections when necessary.
This documentation is biased towards top-down learners (And if you’re actually reading this section, you’re probably already a top-down learner yourself!) However, if you’re a bottom-up person, don’t despair. If you have
patience enough to ready only one chapter then read Chapter 6. If you then
get stuck you may use this manual to search for specific solutions. Most of
the icons and pushbuttons in the software have tooltip strings attached to
them. Simply point the mouse over a button and you will have feeling on
what purpose it has.
If you do not want to read the manual at all, you can instead see the on-line
video tutorials. They are available under the Help menu.
3
3 Conventions and
Abbreviations
This chapter describes the typographic conventions and used abbreviations
in this manual and in the program.
3.1
Typographic conventions
A
Ctrl-A
*.mat
C:/Program
File
File→Save As
Close
} Endocardium
Single frame
3.2
Key A at the keyboard.
Control key. Hold down Ctrl key and A simultaneously.
Icon in toolbar.
Filename extension.
Folder.
Menu, e.g. File menu.
Sub menu, e.g. under the File menu the item Save As is found.
Push/Toggle button in the graphical user interface.
Radiobutton in the graphical user interface.
Checkbox in the graphical user interface.
Trademarks
Below are some of the trademarks used in this manual.
• Segment CMR is a trademark of Medviso AB.
• Segment DICOM Server is a trademark of Medviso AB.
• Sectra PACS is a trademark of Sectra Imtec AB, (http://www.sectra.se).
• Matlab is a trademark of the Mathworks Inc, (http://www.mathworks.com).
3.3
2CH
3CH
4CH
3D
Abbreviations
Two chamber view
Three chamber view
Four chamber view
Three Dimensional
5
CHAPTER 3. CONVENTIONS AND ABBREVIATIONS
3D+T
AA
ASW
ARD
BPM
BSA
CMR
CO
CT
DA
DE-MRI
ED
EDD
EDL
EDV
EF
ES
ESD
ESL
ESV
FWHM
GUI
HR
LV
LVM
MaR
MO
MB
MIP
MPR
MR
MRI
PET
PER
PDW
PFR
PLW
PWV
6
Time Resolved Three Dimensional
Ascending Aorta
Anterior Septal Wall Thickness
Aortic Root Diameter
Beats per minute
Body Surface Area
Cardiac Magnetic Resonance
Cardiac Output
Computed Tomography
Descending Aorta
Delayed Enhancement MRI
End diastole
End Diastolic Dimension
End Diastolic Length
End Diastolic Volume
Ejection Fraction
End systole
End Systolic Dimension
End Systolic Length
End Systolic Volume
Full Width Half Maximum
Graphical User Interface
Heart Rate
Left Ventricle
Left Ventricle Mass
Myocardium at Risk
Microvascular obstruction
Mega Byte
Maximum Intensity Projection
Multiplanar Reconstruction
Magnetic Resonance
Magnetic Resonance Imaging
Photon Emission Tomography
Peak Ejection Rate
Proton Density Weighted
Peak Filling Rate
Posterior Lateral Wall Thickness
Pulse Wave Velocity
3.3. ABBREVIATIONS
ROI
RV
RVmaj
RVmin
SPECT
SSFP
SV
TOF
VENC
Region Of Interest
Right Ventricle
Right Ventricle Major Axis
Right Ventricle Minor Axis
Single Photon Emission Computed Tomography
Steady State Free Precision
Stroke volume
Time of Flight
Velocity Encoding limit
7
4 System Requirements
In this chapter the hardware requirements for the software are outlined. Possible bottlenecks are (in order of likelihood) lack of RAM memory, CPU
speed, and I/O network or disk transfer rates.
4.1
Operating system
Segment CMR is available both as a precompiled application and also a
source code version. Precompiled versions are available for the following
platforms:
• Microsoft Windows. It will run on any of the following Windows 2000,
Windows XP (32 bit), Windows XP (64 bit), Windows Vista (32 bit),
Windows 7 (32 bit), Windows 7 (64 bit), Windows 8.
4.2
Hardware requirements
The list below are the recommended hardware requirements. To run a clinical
versin of Segment CMR you need at least the specifications indicated below.
• A fairly recent computer with 4 GB of memory or more.
• Harddisk with at least 500 MB of available space. The program Matlab Compiler Runtime takes about 450 MB, another 20MB is taken by
the program.
• Graphics card supporting both DirectX and OpenGL (hardware accelerated) is recommended. Systems with two screens is recommended for
clinical usage of Segment CMR.
We strongly recommend using SSD disk for reading data.
4.3
Internet access
To read the Instructions for use in the language of your choice you need
internet access. The instructions are available in the official language for
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CHAPTER 4. SYSTEM REQUIREMENTS
each of the countries where Segment CMR is sold. The english version of the
instructions for use are always accompanying the software package for offline
use.
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5 Loading Image Stacks
The best method to load and manage studies is by using the Patient Database
Module, described in Segment CMR Database Manual. For clinical use, we
discurage the direct use of the DICOM loader since this is a sub optimal
workflow in the clinical situation, instead please look at the Segment CMR
Database and PACS connection Manual.
This section is included in the manual for reference only in case you need to
load from network, CD or a USB stick. We recommend that you for clinical
routine store the patients in the patient database and load them from there.
When loading from CD we strongly recommend you to import the CD to the
patient database, for further details, please see Patient Database and PACS
Communication Manual.
The program can read DICOM, and also an internal file format. The internal
file format (called .mat files) has the advantages that one file may contain
several image stacks along with object contours and measurements, and it is
also much faster and easier to load compared to loading DICOM files.
It is highly recommendable that when an image stack has been loaded from
DICOM files to save the image stack(s) to the internal file format. This
makes it then much easier to go back and reanalyse datasets if necessary.
Note also that the internal file format requires much less storage space that
the original DICOM files, mainly due to cropping of the images and to lossless compression.
How to browse your DICOM data in the easiest way is described in Section
5.1.3.
The file loading dialog box is started from the main menu, under File, or by
pressing Ctrl-O. This brings up the file loader GUI shown in Figure 1.
The file loader process the selected directory and its subdirectories to find
the number of files in that directory. Since this process takes some time this
operation is cached, and creates a file called folders.cache. To recreate
. When reading from a CD-ROM it is recommendable
the cache, press
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CHAPTER 5. LOADING IMAGE STACKS
Figure 1: File loader GUI.
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5.1. LOADING DICOM FILES
to copy the CD-ROM to your hard drive if you will load most of the files on
the CD-ROM, since random file access from CD is very slow and caching is
not possible. For further details on how to import DICOM CD-ROM’s, see
Patient Database Manual.
5.1
5.1.1
Loading DICOM files
Loading DICOM files
When loading DICOM files Segment CMR assumes that the files are sorted
so that each image series is stored into one folder. Each folder may then
contain one or many DICOM files. This is illustrated in Figure 2.
Figure 2: Files needs to be sorted so that each image series are stored into a
separate folder.
If the files are not stored in this fashion then there is a sorting utility available.
DICOM is an loosely structured file format and direct reading from DICOM
files is slow. Currently the use of meta DICOM files is not supported (the
DICOMDIR file is simply ignored).
You can either load each image series at a time or use a graphical tool to
select what image stacks to load. The graphical series selector is described in
Section 5.1.3. To load on image series at a time, start by selecting one folder.
To go up one directory level double click on .., or click on the
icon. To
more easily get to a different folder, click on the Browse pushbutton. To go
down one directory level double click on the folder name. Once selected one
folder containing DICOM files a preview of one file in that folder is shown.
To load the complete image stack, perform the following steps:
13
• Start by selecting the imaging technique in the top left corner of the
GUI. The imaging technique sets the default segmentation parameters,
and it is crucial that you select the correct imaging technique. For
many scanners and sequence types this is identified automatically.
• When a valid file/folder is selected a preview of that dataset is displayed. Patient details and acquisition time are also shown.
• It is recommended, but generally not required to select Image Type
and Image View Plane. This tells Segment CMR what kind of image
it is. This might be required for future analysis in some applications.
It is also a good idea to label image stacks upon loading when for
instance doing stress analysis to be able to safely differentiate baseline
from stress exams. For research purposes it is possible to set free text
name as Image Type and Image View Plane.
• Select the desired region of interest size. Usually for normal hearts
100mm is sufficient to cover the left ventricle. Enlarged ventricles will
need 150mm or even more.
• Click Load to start the loading process. This brings up a red box in
the preview image. Position this box with the mouse and left click to
start the loading process. If you want to use a different size of ROI
right click to abort loading operation. Then click again on the Load
button.
• Once positioned the box, left click with the mouse to start loading the
files.
Once all image files are loaded a dialog box opens where you need to confirm
voxel spacing and timing details. How Segment CMR interprets the DICOM
information to calculate these parameters is described in Section 26.2. For
users that do not use images from the three major vendors Siemens, Philips,
or GE should read this section. Further technical details about how Segment
CMR interprets the DICOM files are given in the Segment CMR Technical
Manual.
If heart rate is not present in the DICOM file Segment CMR tries to guess
that based on the time increment and the number of time frames to get R-R
interval. This will fail if your image sequence is for instance one image every
heart beat.
14
5.1. LOADING DICOM FILES
5.1.2 Tips and tricks
Often the files are not stored exactly as prerequisited above, then there are
many tips and tricks available.
• You may select several subfolders. Then the program loads all the files
in the subdirectories. Each subdirectory must have the same number
of files. This is the case for old Siemens files and Bruker Paravision
DICOM files.
• You may select what DICOM files to load directly. Note however that
the files need to form a valid image stack and the result may be incorrect
if slices are missing etc. When you do this, always ensure that the files
are sorted properly.
• It is possible to preview different files by the Position slider.
• To get detailed information about DICOM tags in the files press DICOM info .
5.1.3 Graphical image series selection
The graphical series selector tool is shown in Figure 3. While moving the
mouse pointer over the image series more information on each image series
is shown in the top of the graphical interface. Select which image series to
load with left mouse button. Image series outlined in yellow are selected. It
is also possible to group image series to one image stack. Image series that
are to be grouped are selected by holding down the Shift key while mouse
clicking, or by using the middle mouse button. Thereafter, press the pushbutton Group Selected . Grouped image series are shown with a green outline.
Multiple image stacks can be selected for loading or grouping by clicking and
dragging over the selection. When finished selecting image series, press Load .
To speed up the process this operation the generation of the thumbnails is
cached.
Note that when using this tool to load the image, then there is no cropping of
the images done, and that is highly recommended to crop the images during
the image analysis process. Also note that if multiple directions is detected
in the dicom folder all the different directions are loaded as separate image
stacks.
15
Figure 3: Graphical image series selector.
16
6 Program Overview
This chapter provides an overview of the program. Another good method
is to view the on-line video tutorials. The tutorials are available under the
Help menu.
An example of the main graphical user interface is shown in Figure 4. The
major portion of the user interface is occupied by a viewing area where multiple image stacks can be visualized side by side. The current active image
stack is outlined with an orange thick line. To make another image stack
active, simply click on the image stack with the mouse pointer. A thumbnail
image is shown for each loaded image stack. To view an image stack drag the
thumbnail down to the main viewing area. To scroll through the thumbnails
either use the slider or press Ctrl while scrolling with the mouse wheel.
The upper right corner is occupied with a reporting panel where quantitative details about the current image stacks are shown. There are two rows
of icons. The top row contains icons that applies to all loaded image stacks,
whereas the bottom row contains icons to applies to the current active image
stack only.
Middle right part of the user interface is occupied by a volume curve and
a time indicator. This graph area shows left ventricle volume versus time
(red), left ventricle muscle volume (green), papillary muscle volume (blue).
One easy method to adjust the displayed time frame is by clicking in this
graph. You can also interactively drag which time frame that is taken as
end diastole (ED) or end systole (ES). Just above the volume graph a list
box with assumed long-axis motion is located. In this example the long-axis
motion is automatically calculated under the assumption that the left ventricular mass is constant over time. The program selects the long-axis motion
amplitude that best fits this assumption. Note that this auto detect should
be disabled when manually drawing contours.
If the checkbox Single frame is selected then segmentation and other operations such as translate, scale, and delete are only applied to the current time
frame. To further make the user aware of this change of behavior the box
17
CHAPTER 6. PROGRAM OVERVIEW
Figure 4: Main graphical user interface.
around the currently selected image panel turns to white when single frame
mode is selected.
6.1
Viewing image stacks
To view a non visible image stack simply drag the thumbnail to an image
panel. Right clicking on the thumbnails brings up a context menu where
more options are available. To view all loaded image stacks press Shift-A.
Only one of the image stacks are active at the same time. Around the active
image stack an orange rectangle is drawn, both in the main image drawing
area, and around thumbnail image.
Image stacks can be viewed in four different modes; one slice view, montage
view, montage view in rows. The different modes are selected with the icons
(one slice),
(montage or all slices),
(montage view in rows). Each
of the different viewing modes will be described in details below. It is possible to view the same image stacks in different viewing modes simultaneously.
The number of image panels can be selected by the icons
18
6.2. MONTAGE VIEW
or under the View menu. The icon
views information about the patient.
It also also possible to enter/adjust the patient information. Commonly this
is used to add patient height to be able to calculate BSA.
The icon
brings up an interface for saving and loading user specified
views. This allows users to save their favourite combination of stacks to view
for use with any image set. It is also possible to associate each saved view
with a specified hotkey. When loading a saved view for a new image set,
Segment CMR automatically looks for the best matches among the current
image stacks, taking into account such properties as image type, view plane,
time resolution, etc.
controls the visibility of pins, conThe section
tours from other image stacks, endo / epicardium contours, region of interests, delineated infarct regions, measures and annotations, center point, and
image plane intersections, respectively. The icons
and
zooms in/out
the current active image stack. The icon
refreshes the screen which might
be very useful since it also refreshed the GUI which under certain circumstances might ’hang’ in case of calculations that went wrong. If the GUI
seems irresponsive it is well worth to try refresh the screen. The icon
resets the light/contrast setting. The icon
automatically sets which sets
contrast and brightness so that an upper and lower percentile of the intensities get saturated. The icon
undo the latest contour editing command.
shows information about the current image stack.
The icon
6.2
Montage view
Figure 5 shows a screen-shot of the program in the most common view (montage view), selected by the icon . You can also switch between the montage
view and the single slice view by using the hot key v. In the montage view all
slices in an image stack are displayed. The slice(s) with a yellow box around
are selected. Automated segmentation and many other operations are only
applied to selected slices. Slices are selected by activating the tool
, and
by left mouse click on the desired slice and drag the mouse while the left
button is hold down.
19
Figure 5: Screen-shot of the program showing an image stack in montage
view.
20
6.3. MONTAGE ROW VIEW
6.3
Montage row view
The montage row view is same as the montage row, but with the difference
that the slices are shown to minimize the number of rows that are used to
display the entire image stack.
6.4
One slice view
In one slice view only one single slice are shown at a time. You can then
browse between slices by up/down arrow keys. Right and left keys displays
next and previous time frames. In this view intersecting image planes that
also are shown. The intersection are indicated with a white or an orange
line. Orange line indicate intersection with the current active image panel.
. In this view intersecTo hide/view the plane intersections use the icon
tions with contours drawn in other image stacks are also shown. For instance
if the short axis stack is segmented the contour will also be visible in the long
axis image. This is illustrated in Figure 6. This is very useful to delineate
structures that might be difficult to see in only one image plane. The contour
. The contour intersections
intersections can be hidden by using the icon
are only visible in one slice view mode. Note that different breathing position
may cause the image stack not to align properly.
6.5
Viewing velocity encoded image stacks
For velocity encoded images it is possible to view both the magnitude image
and the corresponding velocity encoded image(s). In the thumbnails a white
box is drawn around magnitude and phase image to indicate what image
stacks belong to each other. For more details see Chapter 12, Flow Analysis.
6.6
Playing images as a cine-loop
controls what time frame of
In the main icon toolbar the
the image sequence is displayed. The icon
(Shift-Left Arrow) shows
previous frame and applies to all visible image stacks. It displays the previous
frame for the current image stack, and tries to find the corresponding time
frame for all image stacks. If you just press Left Arrow then it just change
time frame for current image stack. The icon plays all image stack sequence
21
Figure 6: Contours are visible in other image stacks as dots. This is very
useful to delineate structures that might be difficult to see in only one image
plane.
as a cine loop. The icon
(Shift-right) performs the same operation as
, but forward in time instead. Control and arrow keys show previous/next
increases the playback speed, and
frame for all image stacks. The icon
decreases the speed. Another convenient method to quickly move between
time frames is by clicking in the volume graph. Here you can also interactively
drag which time frame is used as end diastole (ED) or end systole (ES). You
can also switch between systole and diastole by using the hot keys d and s,
respectively. Yet another way to scroll between time frames is to use the
mouse wheel and at the same to press Shift. The icon
allows the user
to perform manual delineations while the current slice is played. This is very
useful for a better understanding about for instance the papillary muscles.
6.7
Synchronizing image stacks
It is often required to synchronize image stacks in time and slice. This can be
done by using the Shift-key. Shift-left/right key shows previous/next frame
and synchronizes all visible image stacks in time. For image stacks that have
different number of time steps the nearest time frame is shown. Shift-S and
Shift-D toggles between systole and diastole in all visible image stacks.
22
6.8. LOADING AND STORING IMAGES
6.8
Loading and storing images
The top left section of icons contains functionality to load and save image
data. The first icon
opens a file loader GUI described in Chapter 5.
The second icon
opens the patient database described Segment Database
Manual. The third icon
saves all the loaded image stacks to one file. The
opens a connection to a PACS server, see Segment Database
fourth icon
Manual.
6.9
Tool palette
The tool palette is located at the lower right corner of Segment main graphical user interface. The tool palette have several modes in which different
tools become available. The current mode is indicated as black text on blue
background. The current active tool is indicated by displaying the tool in a
darker gray color. Generally, with few exceptions all functions in the program
only applies to selected slices. Selected slices are indicated with a yellow box
in the montage view. The functionality of selecting slices can only be used
in the montage view. An alternative to select slices is to use the short key
and move
Ctrl-A that selects all slices. To pan the image use the tool
the mouse.
There are some general tools that is present in all tool modes, and these
are;
to undo last contour edit command,
to adjust brightness and
contrast (Hold down the mouse button and move left right to adjust contrast
to select slices or image stacks. This
and up/down to control brightness),
latter tool is the default tool. Contrast and brightness can also be adjusted
, by using the middle mouse button instead.
without first clicking the icon
There are also in some of the modes
that translates ROI’s and contours
or the whole image if no ROI or contour was clicked, and
that scale ROI’s
and contours.
6.9.1 Left ventricle tools
The left ventricle tools are shown in Figure 7. Colors are used to indicate
endocardium (red) or epicardium (green).
On the first row (from left to right);
automatically segments both endocardium and epicardium of the left ventricle. You need to ensure that the
23
Figure 7: Left ventricular toolpalette.
center ’+’ is in the middle of the ventricle and that all slices that covers the
left ventricle are selected, see Chapter8. The second icon
automatically
autosegments the endocardium in the selected slices. The third icon
matically segments the epicardium of the selected slices. The fourth icon
attempts to remove the papillary muscles. This can be use multiple times to
successfully remove them.
On the second row (from left to right): The first icon
is used for an
interpolated contour mode to click out points to control the endocardial
contour. To close the contour and interpolate a line between the points, shift
click in the image. The points can interactively be dragged. The second
is used to manually draw the endocardium. The third tool
is
tool
is a tool to
to automatically refine the endocardium. The fourth tool
propagate the segmentation to next time frame.
On the third row is the same as the first row except that the tools applies to
the epicardial contour instead of the endocardial contour.
The space key can be used to toggle between the endo and epicardial tool
counterparts.
6.9.2 Right ventricle tools
The right ventricle tool palette is shown in Figure 8. The icon
is used
to click out points in the interpolated contour tool for the right ventricle
endocardium, and
is used for the epicardium, respectively. The icon
24
6.9. TOOL PALETTE
is used to manually draw the right ventricle (RV) endocardium. The icon
is used to automatically delineate the RV endocardium. Note that the RV
is used to refine the
tool is not as automated as the LV tools. The icon
RV endocardium. The icon
is used to manually draw RV epicardium.
Figure 8: Right ventricular toolpalette.
6.9.3 Viability/Scar tools
The functions described in this section is in US only for off label use and for
investigational use.The viability tool palette is shown in Figure 9.
Figure 9: Viability toolpalette.
The icon
is used to automatically delineate infarct region on MR delayed
enhancement images. The icon
is used to manually delineate infarction.
25
The icon is used to manually delineate regions with microvascular obstruction. The icon
manually removes infarction. The icon
erase manual
corrections of infarction. The show the manual interactions and regions of
microvascular obstruction you need to press the key o to toggle the display.
6.9.4 Miscellaneous tool mode
The miscellaneous tool mode is shown in Figure 10.
Figure 10: Miscellaneous mode toolpalette.
The icon
is used to place annotation points. The icon
is used to
make length measurements. Left click with mouse at the starting point and
hold mouse button down and move the mouse to end point. It is possible
is used to
to interactively drag and refine measurements later. The icon
is used to automatically crop all
crop the current image stack. The icon
image stacks to focus on the heart, in order for it to work properly at least
one time resolved short axis image stack is required. The icon
allows you
to find positions in 3D space for all visible image stacks.
6.9.5 ROI tool mode
The toolpalette for region of interest analysis (ROI) is shown in Figure 11.
The first tool
is used to manually delineate region of interests. The icon
is used to automatically outline a vessel from scratch. Before using this
place the center point (+) in the middle of the vessel. The icon
refines
a vessel. This is done in all time frames if the checkbox Single Frame mode
is unchecked. The icon
copies the ROI contour to next time frame and
26
6.10. GENERAL VIEW AND REPORTING FUNCTIONALITY
Figure 11: Region of interest mode toolpalette.
refines it. The icon
tracks a ROI over the entire cardiac cycle. The icon
selects current color to use to draw ROI’s. The icon
is used to name
the current ROI.
6.10
General view and reporting functionality
The report tool
creates a full text and graphical report of all the measurestarts a movie recorder that allows to
ments for all image stacks. The icon
store an image stack as an .avi movie. It is also possible to directly export
a movie under the Export menu.
There are seven tools available to visualize or handle image stacks. Each of
these starts separate graphical user interfaces to view and manipulate image
data. They are all available as icons on the main menu.
starts a tool to do multiple planar reconstructions. The icon
The icon
starts a three dimensional visualization tool. The icon
starts a tool
to do regional wall motion per slice analysis described in Section 11.2. The
icon
starts a tool to do bullseye visualization of wall motion and infarct parameters. The last icon
starts flow analysis tool, described in
Chapter 12.
27
7 Measurements and
Annotations
The whole software package Segment is designed for quantitative analysis
and subsequently there are a rich variety of measurement tools available.
7.1
Length measurements
There are two possibilities to make length measurements. The easiest method
is to use the measurement tool
. To place a linear measurement, left click
with the mouse, hold mouse button down and drag mouse to the desired
location. Alternatively, or to place a measurement consisting of several line
segments, hold down the Shift key while clicking to place end-points. Finish
by clicking with Shift released. You are then asked to annotate and give the
measurement a label. It is possible to refine the position of the measurement
by click one of its end-points and drag that to the desired position. The
measurement with its annotation is shown in Figure 12.
Figure 12: Example of a measurement of the left ventricle diameter.
29
8 Segmentation of the Left
Ventricle
Before starting to describe segmentation of the left ventricle it is of importance to define what do we consider as the left ventricle.
8.1
Definition of the left ventricle
At a first thought it seems very easy to define what part of the heart should
be included in the left ventricle. At a second thought the definition needs
to be practical and repeatable. In the program the following decisions have
been made.
8.1.1 Papillary muscles
By using the automatic LV segmentation algorithm, the papillary muscles are
removed as much as possible (even if they are attached to the wall). Details
on how to manually include/exclude the papillaries are given in Section 8.3.
8.1.2 Mitral annulus
Long-axis motion of the left ventricle is a very important component to
achieve correct ejection fractions, and volumes. Long-axis motion is accounted for in the automatic LV segmentation algorithm. The long-axis
motion direction is assumed to be orthogonal to the slice direction. The
long-axis direction is shown in Figure 13. In the most basal LV slices the
algorithm defines the LV segmentation with the long-axis motion in mind.
8.2
Start the segmentation process
Before starting the automatic LV segmentation process, make sure that the
basal-apex orientation is correct. The most basal slice should be in the upper
left corner. If not then select Image Tools→Flip z and x, as described in detail
in Chapter ??. Also make sure that correct Image Type is selected when
loading the image stack (MR SSFP, CT...). This can also be set afterwards
by right-clicking on the image stack thumbnail image and select Set Image
Description. If the checkbox Single Frame Mode checkbox is checked, a
31
CHAPTER 8. SEGMENTATION OF THE LEFT VENTRICLE
Figure 13: Three dimensional view of the left ventricle showing the long-axis
direction.
message box questioning if you would like to perform LV segmentation in all
time frames is asked. It is recommended to do the LV segmentation in all
time frames since this leads to better conditions for the segmentation algorithm. However, you can select to only perform the LV segmentation in the
selected time frame.
in the LV mode.
In order to start the segmentation process click on
A new interface is open, according to Figure 14, where you select the most
basal slice and the most epicardial apical slice of the LV. The basal limit
should be the most basal slice that have left ventricular myocardium at least
in some part of the heart cycle. If long-axis image stacks are available, the
slice selection can be reviewed in the long-axis views. In order for Segment
CMR to find the long-axis image stacks, the Image View Plane have to be
defined as 2CH, 3CH or 4CH. The Image View Plane is defined by right click in
the thumbnail preview and select Set Image Description. The next step is
to ensure that the LV center cross is correctly defined in the middle of the LV
lumen. This is done by review, and if needed adjust, the orange cross in the
short-axis view. The center cross should be in the middle of the LV lumen
for the midventricular slice and the placement in the basal and apical slices
is irrelevant. After the selection of LV slices and definition of LV center, the
automatic LV segmentation is started by click on Start LV segmentation . The
final result from the automatic LV segmentation algorithm is then displayed
in the main interface for Segment CMR. If needed, manually adjustment of
the LV segmentation is performed in the main interface according to Sec32
8.3. EDIT THE SEGMENTATION RESULT
tion 8.3.
Figure 14: Interface for LV analysis.
8.3
Edit the segmentation result
Unfortunately the segmentation result is not always as one would desire. We
have done as much as we possible can to implement and design a segmentation algorithm that is robust and accurate, but despite that the algorithm
do fail in certain cases, and especially on the epicardial contour.
There are many implemented methods to manually edit the segmentation
result. Different methods are good in different situations. I recommend to
learn them all, and by experience learn in what situations the different types
of manual interaction works best. If you experience that editing is a cumbersome task, then you are probably doing it the wrong way.
When the segmentation fails completely, please check the following items:
33
• Double check that correct slices are selected for the LV segmentation
and that a good LV center point is chosen.
There are several methods to manipulate the segmentation result. Each
method have different applications where they work better, and it is a learning process to learn which tool to use in different situation.
8.3.1 Undo segmentation
To undo the latest segmentation operation select undo from the tools menu,
or using the undo icon
, or using the hot key Ctrl-Z.
8.3.2 Refine segmentation
Refine runs the segmentation algorithm a few iterations, and thus further
refines the segmentation. This functionality is chosen by the two icons
and
for endocardium and epicardium, respectively. Note that the optimization
is only run for the selected slices.
8.3.3 Expand or contract segmentation
If the shape of the contours is satisfactory but are inside or outside of the
,
,
or
can be used to expand or
myocardial border, the tools
contract, respectively, the contours. The tools are applyed on selected slices
and expand or contract the contour in a relative manner. If the checkbox
Single Frame Mode is checked, then the tool is only applied in the current
time frame, otherwise in all time frames.
8.3.4 Manually adjusting the contour by interpolation points
Manually correction of the contou by using interpolation points is probably
the easiest way to make changes in the segmentation. This functionality
is chosen by the two icons
and
for endocardium and epicardium,
respectively. If there is LV segmentation in the selected slice, one left mouse
click in the current slice will put interpolation points for the contour. If no
LV segmentation is present in the current slice, a LV segmentation can be
performed by the interpolation points by select
or
tool. Then add
interpolation points by left mouse click and interpolate the contour by shiftclick. The LV segmentation is then corrected by move the interpolation points
by dragging with the left mouse button and hold it down. New interpolation
34
8.3. EDIT THE SEGMENTATION RESULT
points can be added by left mouse click in at the position where you like to
add the point.
8.3.5
Manually drawing the contour
This functionality is chosen by the two icons
and
for endocardium
and epicardium, respectively. Use the left mouse button and hold it down to
manually draw the complete contour or correct an existing contour. If the
checkbox Single Frame Mode checkbox is checked, then the segmentation is
only performed in the current time frame, otherwise in all time frames. A
quick method to toggle between drawing epicardium, and endocardium is to
use the space button on the keyboard.
8.3.6
Translating the segmentation
The segmentation can be translated/dragged in each slice. This is done by
in the toolbar palette. Note that the usage of this translausing the icon
tion is especially useful in conjunction with the import segmentation option
in the main menu. Then a segmentation from one imaging technology can
be overlaid an image of a different image stack if they were acquired using
the same coordinate system. A practical application is doing the segmentation on cine gradient echo or cine SSFP images and overlay that result over
late enhancement images. Under the segmentation menu it is possible to
translate/move selected slices towards the base/apex.
8.3.7
Scale the segmentation
In some slices, and typically the apical slices scaling the segmentation can
tool. Scaling
be very effective correction. Scaling can be done with the
can often successfully be combined with the refine operation.
8.3.8
Manually include/exclude papillary muscles
One approach to remove papillary muscles is to perform a few iterations
with the refine tools for the LV segmentation according to Section 8.3.2. The
papillary muscles can also be included/excluded in the LV segmentation by
using the manual drawing tools according to Section 8.3.5.
35
8.3.9 Removing segmentation result
The segmentation result can be removed with the right mouse click popup menu (shown in the place pin section above). These function are also
available in the main menu under Segmention.
36
9 Segmentation of the Right
Ventricle
The right ventricle is much more geometrically complex than the left ventricle. The walls are much thinner and there are more and complex trabeculation. This is one explanation that there are currently in Segment CMR no
really good automated tools to do segmentation of the right ventricle. This
will be improved in future versions of Segment CMR.
Currently what is available are the same basic functionality as for the left
ventricle. For the mid ventricular slices the automated methods (manual
draw+refine can be used).
At the current stage we do not recommend to do time resolved segmentation
of the right ventricle since the drawing and edit tools are so poor. We would
the suggest to remove all RV segmentation except systole and diastole. An
example of segmentation of the right ventricle is shown in Figure 15.
37
CHAPTER 9. SEGMENTATION OF THE RIGHT VENTRICLE
Figure 15: Top: Segmentation of the right ventricle in diastole in a short
axis image stack. Bottom: Segmentation of the right ventricle in systole in
the same short axis stack. Note the relative large long axis motion.
38
10 Segmentation of Long Axis
Images
Segmentation of the left ventricle (as well as any other chamber) can be done
by manually outlining the object in longaxis images. This is a fast alternative
to manual drawing on short axis images.
Contours need to be present in at least two image stacks labeled 2CH, 3CH
or 4CH to enable volume calculations. Please note that the image stacks
needs to be labeled view the correct view. To label the images right-click
on the thumbnails and select Set Image Description. Figure 16 illustrates the
concept of segmentation in long axis images.
10.1
Click an image to show point location in all views
To provide a better estimation of the three dimensional volumes when drawing in longaxis images, there is a tool that allows the user to click an image
to show the location of the clicked point in every active view. This tool
is found in the Misc toolbox.
39
CHAPTER 10. SEGMENTATION OF LONG AXIS IMAGES
Figure 16: Illustration of the process of drawing segmentation in long axis
images.
40
11 Regional Wall Analysis
There are a number of different analysis options available to make regional
wall analysis. Please note that for regional wall motion analysis the common
clinical practice is to exclude the papillaries from the segmentation, for more
information on how to include/exclude the papillaries, see Section 8.3.
There are three different visualization options available for wall motion analysis:
• Radial contraction versus time
• Report per slice (icon
• Bullseye plots (icon
11.1
)
)
Radial contraction versus time
In this option the regional contraction velocity per segment is plotted over
time. On the y-axis on each plot is the slices (basal to apical), and on the
x-axis is time. An example is shown in Figure 17.
11.2
Report per slice
It is possible to do regional wall motion analysis on a slice by slice basis.
. Possible parameters to plot are wall
This tool is started by the icon
thickness, fractional wall thickening, radial contraction velocity, and radius.
An example showing wall thickness over time is shown in Figure 18. .
41
CHAPTER 11. REGIONAL WALL ANALYSIS
Figure 17: Radial velocity versus time in six sectors. Note the apical to basal
gradient in the onset of the radial contraction.
Figure 18: Wall thickness over time in a healthy subject.
42
12 Flow Analysis
This functionality may depend on your MRI scanner. Currently it has been
tested using Siemens, Philips and GE scanners.
When flow image stacks are displayed, the screen should now similar to what
is shown in Figure 19. On the left image panel the magnitude image is shown
and on the right image panel the phase image is shown. When a flow image
stack is selected a white frame around both the magnitude image and phase
image is drawn in the thumbnail preview area. This helps to keep track of
which phase images belongs to which magnitude images.
Figure 19: Example of main GUI in flow mode.
12.1
Automatic segmentation of flow ROI’s
The suggested method is to select the ROI tool . Then draw a ruff outline
of the vessel contour. Thereafter start the automated vessel tracking and
refine. This is done by pressing Ctrl-T.
Another method to automatically segment a vessel is to drag the center cursor
(white +) to the approximate center of the desired vessel and press Ctrl-G,
43
CHAPTER 12. FLOW ANALYSIS
or Auto delineate a vessel under the Segmentation→ROI and Flow Tools menu.
The vessel is automatically delineated and you are asked for an appropriate
label.
12.1.1 Refine
Refine operation operates on the current time frame or all time frames depending on the checkbox Single frame mode . Short key for the refine function
is Ctrl-R. You need to have the ROI pen active when using the hot key. Refine on all time frames is particularly useful if the vessel is fairly round and
not to close to other surrounding tissue.
12.1.2 Refine and propagate
Start at the first time frame of the time series. If pleased with the result
simply use the right arrow key on the keyboard to proceed to next time
frame. When you find a time frame where you are not pleased with the
to adjust the contour or use the refine
segmentation use the ROI pen
option Ctrl-R with the checkbox Single frame mode enabled. Continue by
propagating the contour by pressing Ctrl-F.
12.1.3 Shrink flow ROI
If the RIO is outside the vessel then it might be advantageous to shrink the
ROI followed by one ore more refine operations. Shrink flow ROI is found
under the Segmentation menu and the submenu ROI and Flow tools.
12.2
Plotting the result of the flow analysis
or by using the
The flow plotting utility is started by using the icon
function Plot flow curves under the Flow menu. An example of the graphical
user interface is shown in Figure 20.
In the upper right area of the GUI you can select which parameter to plot.
The volumes presented in Volume panel of the GUI represents flow integrated between the two vertical red bars. These bar can interactively be
moved with the mouse to control the range of the integration. Forward volume is the volume of the flow integrated only over the time frames where the
net flow is positive (forward). Backward volume is the volume of the flow
44
12.2. PLOTTING THE RESULT OF THE FLOW ANALYSIS
Figure 20: Example of flow plotting GUI. Plotting parameter can be selected
in the upper right corner of the GUI. The flow integration is performed
between the two red bars.
integrated only over the time frames where the net flow is negative (backward). This should be contrasted to the flow parameter Forward/Backward
that plots simultaneously the flow that goes forward and backward of the
region of interest. Note that there can be significant backward flow in one
time frame even though the net flow is forward in that very time frame. An
example on the latter is shown in Figure 21. The sum of the two curves is
the same as the net flow that is shown in Figure 20.
It is also possible to plot the Velocity over time, and this is shown in Figure 22. The ’error bars’ denote the standard deviation of all pixels in the
ROI of that particular time frame.
Another possibility is to plot the max or min velocity in the ROI over time.
It is also possible to plot the radius and diameter over time. The radius are
calculated as; what diameter need a circular vessel have to have the same
area as the area of the ROI. The option Signed Kinetic Energy calculates the
kinetic energy in the blood assuming standard density of the blood.
The final possibility is to plot a 3D profile of the velocity distribution of the
vessel. This can be plotted for all time frames at once or only a single time
frame that later can be stepped forward/backward in time. An example of
45
the 3D plot is shown in Figure 23.
Figure 21: Example of plotting of backwards and forward flow simultaneously. The sum of the two curves will be the net flow showed in Figure 20.
12.3
Compensating for eddy current effects
To get accurate flow measurements it is important to compensate for concomitant field effects such as eddy currents, and Maxwell effects. Ideally
Maxwell effects should be compensated for directly on the MRI scanner since
it can be analytically calculated. Consult your MRI vendor for details about
how this is implemented in your scanner. Note that when compensating for
eddy current effects the image stack should not be cropped upon loading,
since the algorithm need phase information of static tissue in the chest wall
to function properly.
The graphical user interface for compensating for eddy current effects is
shown in Figure 24.
46
12.3. COMPENSATING FOR EDDY CURRENT EFFECTS
Figure 22: Example of plotting of velocity over time. The ’error’ bars shown
the standard deviation of the pixels within the ROI over time.
Figure 23: Example of plotting of a 3D profile of the velocity distribution.
47
Figure 24: Example graphical user interface for compensating of concomitant
field effects. In the left the identified static tissue is the displayed, and in the
middle panel the corresponding phase for these pixels is shown, and in the
right panel the resulting phase correction is shown.
You can select model order, and clear the phase correction. When you are
pleased with the phase correction press Apply to proceed. The function
automatically finds stationary parts in the image by selecting a percentage
of the pixels whose standard deviation of the phase over time is smallest.
The fraction of pixels taken can be controlled by the edit box Percentile. The
image is divided into four quadrants and the algorithm to find stationary
pixels is applied to each quadrant separately. This is done to ensure that
there are about the same number of pixels from each quadrant. Pixels taken
as stationary tissue are shown as red dots in the magnitude image. The
Magnitude slider controls what magnitude the pixels need to have before
being labeled as stationary. By selecting the mode of operation as Static
tissue ROI then ROI’s that are labeled Static tissue are taken as stationary
areas. This is particularly useful when doing phantom experiments, since the
automated identification of static areas fails in cases with stationary flow.
The mode of operation Phantom Experiment (GE-method) automatically
finds a flow image stacks that have the same scanning parameters this useful
when a static tissue have been scanned in the same position as the patient as
48
12.4. PHASE UNWRAPPING
recommended by GE for eddy current compensation. For usage, see paper
by Alex Chernobelsky et al. [?].
12.4
Phase unwrapping
In cases were the velocity in the blood is higher than the VENC the velocities can wrap around. Under certain conditions these phase wraps can be
uncovered and phase unwrapping can be performed to retrieve the correct velocities. The graphical user interface for the phase unwrapping tool is shown
in Figure 25.
The checkbox Show ROI pixels shows the pixels that are used in the ROI in
a red color. This is useful when one want to know exactly what pixels are
included in the ROI. The checkbox Use magnitude mask is used when one
want to limit the automated phase unwrapping only in pixels that have a
magnitude over a certain threshold.
12.4.1
Automated unwrapping
The automated phase unwrapping algorithm works on a pixel by pixel basis
and operates along the temporal dimension. It looks for pixels where the
phase appears to have wrapped once up and once down. Therefore the algorithm will fail for a biphasic velocity profile if phase wrapping occurs at both
phases. Furthermore, it only considers single wrap arounds (i.e the phase is
assumed to have wrapped once).
12.4.2
Manual unwrapping
. The tool
is used to pan the
There are four tools available,
images. The second tool
wraps the pixel up at left mouse button clicks.
The third tool
wraps the pixel down at left mouse button clicks. The
fourth tool
is used to plot the phase of the current pixel over time. This
is mainly useful for debugging purposes. It is possible to zoom the image
. Undo last operation is done by pressing
by usage of the zoom icons
Ctrl-Z or the icon
.
49
Figure 25: Example of the graphical user interface for phase unwrapping.
The left image panel shows the original phase, and the right image panel
shows the unwrapped phase. The long slider adjusts the current time frame.
50
12.5. CREATING ANGIO AND VELOCITY MAGNITUDE IMAGES
12.5
Creating angio and velocity magnitude images
It is possible to create a so called angio image that is the magnitude image
times the velocity magnitude. This is available under the Flow menu and
Create Angio. If you have more than one velocity encoding direction it is
possible to create a velocity magnitude image that is the square root of the
sum of squares of all velocity directions (velocity magnitude).
12.6
Coupling magnitude and flow images
If magnitude and flow image stacks have been loaded into Segment CMRwithout being coupled to each other, it is possible to couple them using the
Couple Magnitude/Phase Flow Image Stacks from the Flow menu. Available
magnitude and phase image stacks are then identified and coupled using
heuristics.
51
13 Bulls eye Analysis
The parameters that currently can be plotted as bulls eye plots are:
• Maximal expansion velocity
• Maximal contraction velocity
• Expansion velocity at PFR
• Contraction velocity at PER
• Maximal wall thickness
• ED wall thickness
• ES wall thickness
• Wall thickening (difference wall thickness ES-ED)
• Fractional wall thickness
• Myocardium volume
• Myocardial intensity (normalized or unnormalized values)
• Scar transmurality
• MaR transmurality
• Data from clipboard (each row is one slice, and each column a sector)
The graphical user interface for creating bulls eye plot is shown in Figure 26.
The orientation of the bulls eye plot can be adjusted by a slider, and the
number of sectors with a list box. Note: it is important to adjust the rotation correctly, so that the sectors corresponds with the correct anatomy. For
correct AHA plots, one need to adjust the rotation so that the longest spoke
in the lower right part of the GUI points to the middle of Septum wall.
The images on the right side of the GUI display one slice of the shortaxis
image from which the bullseye data is extracted. The slider on the right of
the image can be used to change to an image of a different slice. If a longaxis
image is available, it will be displayed in the image above the shortaxis slice
image. This longaxis image will contain intersection lines of the slice planes
included in the analysis (displayed in white), with the current image slice in
53
CHAPTER 13. BULLS EYE ANALYSIS
Figure 26: GUI used to create bullseye plots.
yellow. If This slice only is checked, the current image slice changes to red
and the bullseye plot data is taken only from this slice.
It is also possible to export the results of the bulls eye plot to clipboard (to
later past it into for instance Microsoft Excel). Note that only selected slices
are plotted in the bulls eye plot. For further improve flexibility of editing and
exporting it is possible to plot the bulls eye plot in a separate window. There
are three possible modes of bulls eye plots, one with regular with uniform
sectors displaying the ’mean’ or nominal value for each sector, and one mode
where the bulls eye plot is smoothed, and the final mode where the data
is presented according to the AHA association model [?]. In order to make
the AHA presentation meaningful you should have selected the whole LV.
The smoothed bulls eye plot is done using cubic interpolation over Cartesian
coordinates. The possibility to plot data from the clipboard enables to plot
data as bulls-eye plots that was not created with Segment.
54
14 T2/T2* Quantification
Module
In magnetic resonance (MR) imaging, T1, T2 and T2* relaxation times represent characteristic tissue properties that can be quantified with the help of
specific imaging strategies. The purpose of the T2/T2* Module is to quantify T2 and T2* relaxation times in MR imaging. Quantification of T2 and
T2* values follows the same underlying mathematical principles, but different source images are used.
T2* changes have been shown and quantified under pharmacological test in
coronary artery disease [?], quantification of iron overload and of the heart
and liver in Thalassaemia major [?].
T2* values can be quantified by varying when the same image is acquired
using different echo times.
14.1
Module overview
An overview of the T2/T2* quantification module is shown in Figure 27.
The top left image panel shows the magnitude images for the different echo
times, adjustable with the echo time slider. The lower left panel allows to
make regional restriction on what regions to quantify. There are three modes
and in the first mode Use only myocardium the pixels inside the myocardium
is included in the quantification. The second mode Use only ROI includes
only pixels that are inside region of interests. In the last mode Use full image
all pixels are included in the quantification. The delineation of ROI’s and
myocardium is taken from the last time frame in the image series. The right
image panel shows the pixelwise T2* values.
55
CHAPTER 14. T2/T2* QUANTIFICATION MODULE
Figure 27: GUI for quantification of T2/T2* values. The top left image panel
shows the magnitude images for the different echo times, adjustable with the
echo time slider. The right image panel shows the pixelwise T2* values.
56
14.2. IMPLEMENTATION
The right lower panel shows the fittig curve over time. The mean T2*
value is presented in the graph and the associated graph title. The region
for the mean value calculation is according to the selection of the checkboxes
to the right, either T2* ROI-fit or T2* pixel-fit. The T2* pixel-fit takes
the T2* values according to the blue cross in the right image panel.
T2* values can be exported to spreadsheet by using the Export button.
To create the T2* image stack in the main GUI of Segment CMR use the
Create Image Stacks button.
14.2
Implementation
The detailed implementation of the T2/T2* calculation in given in Chapter 26. In short the calculation is performed with standard exponential curve
fitting that is calculated in the least square sense.
14.3
Validation
The module has been validated comparing to the open source software MRmap
[?]. More validation details is available in a separate report from Medviso
AB.
57
15 Strain Analysis
15.1
Velocity Encoded Imaging
The strain analysis module uses velocity encoded MR images to calculate
myocardial strain. The module have been written by Helen Soneson as her
Master thesis work [?], and resides on the work by Erik Bergvall for strain
calculations and myocardial tracking [?]. This module is not available yet
to researchers since it is under development and will be released as soon as
the underlying method is properly published. Preliminary results about the
method was presented at SCMR 2008 [?],[?].
Strain calculations require velocity encoded MR images with two velocity
components. An example of such an image stack are shown in Figure 28.
The leftmost panel is the magnitude image stack the two rightmost are the
velocity image stacks.
Figure 28: Example of a velocity encoded magnitude image stack and two
directional velocity encoded image stacks.
Before starting strain calculation the myocardium of the left ventricle
need to be manually outlined in end-diastole. One method to do this is to
use the endocardium tool
directly in the velocity encoded image stack.
One tip before outline the myocardium in a long-axis image is to first set the
”Number of points along the contour” in Preferences under the Preferences
menu to 300. This make it easier to do small changes in the segmentation.
The other method is to segment the myocardium in the anatomical (balanced
59
CHAPTER 15. STRAIN ANALYSIS
or SSFP) image stack and then exported it to the velocity encoded image
stack. The exportation is done with the function Import From Cine Stack
under the menu Strain From Velocity Encoded Imaging under the Strain menu.
Before calculating strain the image type have to be set to either ”Strain
2CH TFE” or ”Strain 2CH FFE” (and similar for 3CH and 4CH). This is
done either upon loading or by right clicking on the corresponding thumbnail
images and select Set Image Type.
15.1.1 Strain calculation
The strain in a long-axis velocity encoded image stack is calculated by using
the function Strain Tool under the Strain From Velocity Encoded Imaging under Strain menu. Note that you need to manually outline the myocardium in
end-diastole first. The function calculates segmentation and strain in all time
frames. It also opens a new graphical user interface that make it possible to
analyse/visualize strain in the image. An example of such a GUI can be seen
in Figure 29.
Figure 29: Example of the strain GUI.
To select which strain or displacement parameter to analyse, mark one of the
parameters in the listbox in the figure. The 4 alternatives are:
60
15.1. VELOCITY ENCODED IMAGING
• Total Strain
• Radial Strain
• Longitudinal Strain
• Shear Strain
To see how strain changes over time there are three buttons in the figure
to use. Prev that step one time frame backward in the heart cycle. Next
that step one time frame forward in the heart cycle and Play plays a movie
of strain over the whole heart cycle. The buttons Min and Max produce a
figure of minimal respectively maximal strain in each pixel over time.
The Export button export strain values to a clipboard. These values are
only given section-wise, and the values in each sector corresponds to the
mean value of the pixels in the sector. The sectors are divided according to
American Heart Associations 17-segments model.
15.1.2 Corrections of the segmentation
To make manual corrections in the calculated segmentation select use left
mouse click in the image to move contour points. Delete manual point by
right click on the added point. When you are satisfied with the manual
correction in all time frames push the Retrack button. The Delete button
deletes all manual corrections.
15.1.3 Strain analysis
One method to evaluate the strain calculation is to export the segmentation
from the velocity encoded image stack to the SSFP image stack after the
strain calculation is done. This is done with the button Import From Strain.
The motion of the myocardium can then be compared to the myocardial
movement in the SSFP image stack. It should be noticed that the two images (SSPF and velocity encoded) are not acquired during the same heart
beat which can result in differences in position of the myocardium.
With strain calculated in the current velocity encoded image stack it is possible to produce a graph over time for strain by the button Graph.
61
CHAPTER 15. STRAIN ANALYSIS
In a file that consist of velocity encoded image stacks with calculated strain
in all the three long-axis views it is possibly, by clicking the icon of a bullseye
plot to produce a bullseye plot of strain.
The function Export From Multiple .mat Files under the menu Strain From
Velocity Encoded Imaging under the Strain menu export strain values to clipboard in all .mat files in the selected folder.
62
16 Viability Analysis
The functions described in this chapter is in US only for off label use and for
investigational use.
The viability tools can be found under the MR menu in Segment CMR. The
method used for automated delineation of infarct is described in [?]. It uses
a new paradigm in analyzing delayed contrast enhancement MRI. Instead
of treating each pixel as dichotomously infarcted or not infarcted pixels are
weighted with their signal intensity.
The new method delineates a larger area than the previous method [?]. It
should be noted that even though it delineates a larger area, this should not
be compared to manual delineation, since the darker pixels are given a lower
weight. As a graphical illustration of this a pink line is also shown in the
weighted mode. An example of this is illustraded in Figure 30. This line
graphically represent the corresponding non weighted area. Please note that
this line is only provided for visual feed-back and should not be used for any
quantification purposes. The weighted scar delineation method is extensively
validated in animals, computer phantoms and 40 patients on images acquired
both on Siemens and Philips MRI scanners.
The first step to do viability analysis of delayed enhancement MRI (DEMRI) images is to delineate both endo- and epicardium. This can be done
either manually or by a semiautomated method. In many cases however, it
may be faster to manually draw the endo- and epicardial contours. Then
select Auto Delineate Viability (Weighted method) to delineate infarct. The
automated delineated infarct is now shown with a yellow contour. After the
delineation you can select the mode of operation. The default mode to use
is the weighted automatic scar delineation (see below for details).
In the Viability menu you can select mode of operation, reset all scar delineation, reset user corrections, control visibility and automatic parameters.
and remove
It is possible to add infarct regions by using the pen tool
infarcts with the rubber tool
regardless of the mode of scar delineation.
removes the manual corrections made with the
or
. By
The tool
default manually added scar regions shows up in green and manually deleted
63
CHAPTER 16. VIABILITY ANALYSIS
Figure 30: Example of scar delineation in the weighted mode. The yellow
line denotes the complete affected area, and the pink line a graphical representation of the corresponding weighted area.
64
16.1. GRAYZONE ANALYSIS
areas in blue. The tool
is used to manually draw regions of microvascular
obstruction. Microvascular obstruction is indicated in red. User interaction
(and microvascular obstruction) can be showed/hided by clicking the key
o. Note when using the weighted method, regions with microvascular obstruction needs to be manually drawn if not automatically detected, since
otherwise they are weighted incorrectly. It is also possible to remove regions with microvascular obstruction with the toggable menu option Remove
microvascular obstruction.
16.1
Grayzone Analysis
The menu item Gray Zone Analysis enables the user to divide the scar area into
core and grayzone based on the scar segmentation. The result is displayed
in the image view as colored overlays of dark red (core) and dark yellow
(grayzone) pixels. The quntitative core and grayzone values are presented in
a message box.
65
17 Myocardium at Risk
Analysis
The maR tools can be found under the MR menu in Segment CMR. The
method used for automated delineation of MaR is described by Sjogren et
al [?]. It uses an Expectation Maximization algorithm to calculate a probability of MaR based on intensity instead of using a threshold and models
of the perfusion territories are used as a priori information to constrain the
segmentation.
The first step to do MaR analysis of T2-weighted MRI (T2w-MRI) images is
to delineate both endo- and epicardium. This can be done either manually
or by a semiautomated method. In many cases however, it may be faster to
manually draw the endo- and epicardial contours. Then select Auto Detect
MaR to delineate MaR. In the graphical user interface choose the culprit
artery in the list box and rotate the yellow line to indicate the inferior insertion point of the right ventricle and press OK. The automated delineation of
MaR is now shown with a white contour.
and remove inIt is possible to add infarct regions by using the pen tool
farcts with the rubber tool . The tool
removes the manual corrections
made with the
or
. By default manually added mar regions shows up
in green and manually deleted areas in blue.
67
18 Perfusion Analysis
The perfusion module is used for performing analysis of perfusion image
stacks. Quotes between maximum upslopes of rest and stress images can be
calculated for each sector of the myocardium.
18.1
Module overview
Before opening the perfusion analysis GUI, make sure to have one open image stack whose image type is set to Perfusion Rest and one whose image
type is set to Perfusion Stress. An overview of the perfusion analysis GUI, as
it appears when launched, is shown in Figure 31. From left to right, each image column contains Stress, Rest, Cine and LGE images respectively. Image
slices are shown with the most basal at the top and the most apical at the
bottom. If the perfusion stacks contain more than three slices, a scrollbar allows the user to toggle between them. Segmentation contours are shown, but
can be disabled by unchecking the Contour box. The Rotate checkbox
is used to set images in rotation mode. This causes the images to zoom in
on the contour, and displays the borders for myocardial sectors as well as a
horizontal yellow line from the center to the left of each image. By dragging
this yellow line, the user can rotate the images to align them properly with
the sector partition. When the mouse button is released, the line will rotate
back to its original leftward position and drag the image with it.
The timebars below the Stress, Rest and Cine images enable the user to step
in time. The Stress and Rest timebars each have one bar labelled Start and
one labelled End. These are used to set the start and end points of motion
correction. They also affect use of the playback functionality, which can be
,
done one image at a time using the playback panel with buttons
and , or making Stress and Rest images play synchronously by using the
Play all button.
69
CHAPTER 18. PERFUSION ANALYSIS
Figure 31: GUI for perfusion analysis.
70
18.1. MODULE OVERVIEW
Once an interval has been set using the Start and End bars and all slices of one
timeframe have been outlined in both Stress and Rest image stacks, hit the
Motion correction button to start the automatic motion correction. This process can take several minutes. The result is shown in Figure 32. If intensity
from the right ventricle or elsewhere spills into the myocardium segmentation
as a result of the motion correction, the contour of the respective image stack
can be adjusted contraction percentages in the Inner and Outer textboxes and
using the Contract Contour pushbuttons labelled Stress and Rest .
Figure 32: GUI for perfusion analysis after motion correction.
The two plots on the right side of the GUI show the upslope curves of the
current sector (selected from the pop-up menu), which are calculated using
a Gaussian filter on the measured values. The width of this filter can be
adjusted using the slider labelled Smoothen curve, making the curve sharper
or smoother. By checking the box Show bloodpool , a curve of the blood71
CHAPTER 18. PERFUSION ANALYSIS
pool is shown in red in the same plot. The bullseye plot below the curve
plots displays the sectorwise quote between the maximum stress and rest upslopes, normalized with respect to the respective maximum upslopes of the
bloodpool curves. The quote values are also shown in text next to the bullseye plot, and can be exported to a spreadsheet by clicking the Export button.
72
19 Pulse Wave Velocity
Analysis
An overview of the Pulse Wave Velocity module is shown in Figure 33.
Upon launch, the module automatically finds the image stack that contains
a measurement labelled Aortic Length and the two flow image stacks that
contain ROI’s labelled Aortic ascending flow and Abdominal aorta. The image
on the left of the GUI shows the image containing the measurement. This
measurement is displayed in yellow and the intersections with images containing flow are displayed as white lines. The plot on the right side shows
the flow curves of the Aortic ascending flow ROI (in blue) and the Abdominal
Aorta (in red). For each flow curve, the tangent of the upslope is calculated
using a Gaussian smoothing function and displayed as a dashed line in the
corresponding color. The sigma parameter of the smoothing function can be
adjusted using the slider on the right of the plot.
Pulse wave velocity is calculated using the length of the Aortic Length
measurement and the time between the upslopes of the flow curves. The
time is measured as the temporal distance from the moment when the tangent of the Aortic ascending flow curve is equal to zero to the moment when
the tangent of the Abdominal Aorta curve is equal to zero. This distance is
displayed as a dotted portion of the black line along y = 0 in the plot. The
values for aortic length, time between upslopes and calculated velocity are
displayed in the GUI and can be exported to a spreadsheet by clicking the
Export button.
73
CHAPTER 19. PULSE WAVE VELOCITY ANALYSIS
Figure 33: GUI for Pulse Wave Velocity Analysis. On the left is the image
containing the measurement of Aortic Length. On the right is a plot of flow
curves along with their respective tangents.
74
20 LV Sphericity Analysis
LV sphericity can be calculated from the Analysis menu.
The sphericity of the left ventricle is defined as the maximum short-axis diameter divided by the length of the ventricle. This calculation is performed
separately for ED and ES and for each of these timeframes, it is required that
there exists LV endocardium segmentation in an open short-axis image stack,
as well as an image stack containing a measurement labelled End Diastolic
Length and End Systolic Length respectively.
The values of diameter and length of the ventricle and the calculated sphericity are displayed in a messagebox and copied to the clipboard, allowing the
user to paste them into a spreadsheet.
75
21 Reporting
The report tool is a report generator is a tool to generate reports of a study.
The tool is started by the icon
or under the Report menu. The graphical
user interface is illustrated in Figure 34. The report can be generated in one
of three formats:
• HTML format. The Generate HTML report is used to generate a HTML
report, complete with images and plots. Each page can be printed and
together they contain a detailed report of an exam. An example of the
final output is given in Figure 35.
• JPEG format. A simplified graphic report, containing only text and
tables, can be created using the Send to PAF button. This report is
saved as a collection of JPEG files for easy upload to PAF. The output
folder can be set in the Advanced System and DICOM settings under the
Preferences menu.
• DICOM format. The simplified graphic report can also be saved as
a collection of DICOM files and automatically uploaded to PACS by
clicking the Save to PACS button.
Hospital logo, patient data, signature field and current date are automatically
included in the report. The checkboxes are used to select which details of
the analysis are to be included in the report. A checkbox is grayed out if
data is unavailable.
• LV Analysis, this section contains a table of global LV parameters and,
if the images are time-resolved, a volume curve.
• RV Analysis, this section contains a table of global RV parameters.
• Scar Analysis, this section contains a table of data from scar analysis
and an image of scar delineation.
• MaR Analysis, this section contains a table of data from myocardium
at risk analysis.
• Flow Analysis, this section contains flow data from phase contrast images and a plot of net flow over time. If there are several image stacks
containing different flow data, one section will be added for each such
stack.
77
CHAPTER 21. REPORTING
Figure 34: GUI for patient report generator.
• Shunt and Valve analysis, this section contains the Qp/Qs ratio and
regurgitant volumes and fractions for the mitralis and tricusp, insofar
as the data necessary for calculation is available.
• Distance measurements, this section contains a table that lists all distance measurements performed on the current set of image stacks.
• 2CH/3CH/4CH Longaxis Image, this section contains a user selection
of longaxis images in end-diastole.
• Shortaxis Image, this section contains a montage view of all shortaxis
image slices in end-diastole with delineations included.
21.1
Configuration
This section describes how the Report Module can be configured.
21.1.1 Hospital logo
This is an image header that is supplied by Medviso AB to each customer
separately. Place this file in the folder where Segment CMR is installed.
78
21.1. CONFIGURATION
21.1.2
Reference values
Reference data used in LV and RV analysis can be selected from a listbox. If
patient age and sex are present in the patient info, the listbox will automatically suggest a suitable set of reference values. If reference data is used in
the report, patient values outside the range specified by the reference data
will be marked in red. The name of the used reference data set will also be
included in the report.
A directory contains each reference data set as a text file with the following
structure:
Name: ’Maceira, Males, Age 30-39.’ %Title to display in listbox.
ImagingType: ’SSFP’ %Describes used imaging type.
LowerAgeBound: 30
UpperAgeBound: 39
Sex: ’M’ %should be either M or F.
LVM: [109 185]
EDV: [121 204] %range
...
EDV BSA: [66 101] % BSA means normalized with BSA.
...
21.1.3
Headings for textual report
There is also a large textbox where it is possible to enter free text comments
on the study. This text is then stored together with the segmentation. A
few formatting tricks can be used in this box:
• To divide the text into paragraphs, enter a blank line between the text
blocks to be used as paragraphs.
• To start a paragraph with a headline in bold print, simply begin the
paragraph with the text to be used as headline, then insert a new line
where the text body is entered.
• To insert a super headline, do the same as above except that the text
is entered in all upper-case letters. A super headline may be followed
by a regular headline.
79
CHAPTER 21. REPORTING
For simplification, standard text templates are supplied by Medviso AB. An
example of such a template is the following:
PATIENT HISTORY
<Enter text here>
GENERAL IMPRESSION
LV function
<Enter text here>
RV function
<Enter text here>
FINAL COMMENTS
<Enter text here>
21.1.4 Reviewing doctor
The final textbox in the GUI allows for including the name of the doctor
performing the analysis and generating the report. If entered, the name of
the doctor appears by the logo image at the beginning and by the signature
field at the end of the report.
80
21.1. CONFIGURATION
Figure 35: Example of a report.
81
22 Export Images and Results
22.1
Export image
Using this option, only the current frame without segmentation is exported
as a file. You need to select file format, and the following formats are supported: .jpg, .bmp, .png (portable network graphics), and .tiff. The
recommended image format to use is .png.
22.2
Export screenshot
Using this option, the current frame including segmentation is exported as a
file. The following image formats are supported: .jpg, .bmp, .png (portable
network graphics), and .tiff. The recommended image format to use is
.png. There is also an option to save the screenshot file to a PACS system.
When preparing images for publication it is often helpful to change the color
of the contours to black/white and increase line width to increase visibility.
This can be done under the preferences menu, see Chapter 23 for further
details.
22.3
Export movies
Exporting movies can be done by either using the built-in movie recorder in
Segment or by exporting the current image stack as a movie (Export Movie).
22.4
Movie Recorder
This is an experimental functionality that take screen captures and store
them in a movie format. The movies can be done in two ways and either to
.avi-files or a sequence of .png files (that later can be converted to different
file formats). In future versions it will also be possible to export to animated
.gif format. You can create movies of the main view, zoom view, 3D plot
view, report per slice view. First select Movie Recorder under the Export
menu. This brings up a user interface shown in Figure 36.
83
CHAPTER 22. EXPORT IMAGES AND RESULTS
Figure 36: Movie Recorder GUI.
The movie recorder is when started unpopulated. To do a first screen capture
force an image update by view next frame. You can now set a crop box
(shown in Figure 36 as a red box), set number of frames to record, and start
to record the movie. Usually you should set the number of frames to record
to the same number of time frames as there are frames in the image stack.
When all frames are recorded then a file selection pop up menu appears and
where you can select storing options. When exporting to .avi files you need
also to select a movie compressor, since all compressors might not be available
on your computer. Personal experiences are that the cine-pak encoder are
pretty stable.
84
23 Customization
This chapter describes how to customize Segment CMR. It is recommended
to set the preferences of which folders to use to avoid browsing each time
you want to load or save a file. The GUI for setting preferences is shown in
Figure 37. It is invoked by using the menu Preferences on the main menu.
Figure 37: Preferences GUI.
There are four panels in total. The top most panels sets default folder locations for loading, and saving, respectively. It is also possible to indicate
which drive / path that corresponds to your CD-drive. Then, the left most
panel sets preferences for editing and drawing contours, the middle panel sets
preferences for regional analysis, and the right most panel sets system preferences. The button Advanced System and DICOM Settings opens a new interface
with settings for base image path for patient database, and DICOM communication parameters. The button PACS Settings opens an interface with
settings for PACS communication.
The option Add pins when adjusting contour controls weather points should be
85
CHAPTER 23. CUSTOMIZATION
placed when manually correcting a contour. This option should be checked
when modifying time resolved images, but unchecked otherwise. Black/White view
plots the endocardium and epicardium with white lines. This is useful for
making screen captures for illustrations that are not printed in color. The
edit box Line width for endo/epicardium sets line width for the contours.
This again is useful for making screen captures. Default line width is 1.
The edit box Distance to contour for adjustment adjust how close to a
contour one need to click before this contour is activate. When using the
interpolate tool it is recommended to set this to quite small, typically 1-2.
The edit box Number of Points Along Contour sets the number of points
that are stored along a contour for endocardium and epicardium. When using automated segmentation this value should be set to 80. When manually
drawing complicated objects this can be set to a higher number.If the option Blind Subject Identity is checked then the program will not show patient
info on screen this is useful for making screen shots etc for presentations. It
is highly useful when doing research and the observer should be blinded to
the patient identity. The edit box Number of visible thumbnails sets the
maximum number of thumbnails visible. When the number of image stacks
exceeds this number a slider will be visible to scroll through all the thumbnails.
The radio buttons Radial profiles from endo/epicardial centroid controls how regional wall measures are placed. The radio button
} Modified centerline method is reserved for future use when the modified centerline method will be implemented. The edit box Number of radial profiles
to evaluate sets the number of radial spikes that are evaluated before sector
means are calculated. For more details on how the regional parameters are
calculated see Chapter 26. The checkbox Include touched pixels in ROI sets
how the edge pixels of a ROI are treated. When selected all pixels that are
touched by the ROI are included. The default behavior is to include only
the pixels where the center of the pixel lies within the ROI.
The checkbox Allow DICOM cache allows creation of cache files for tags in
DICOM files to be generated.
The web browser to be used can be chosen in the drop list by either choosing
a program if it is installed in the default location or choose other to browse
for the program file to use for example select chrome.exe, or firefox.exe.
86
23.1. IMAGE DESCRIPTION SETTINGS
Customization of the Report Module is described in Chapter 21.
23.1
Image description settings
The automatical definition of image description parameters upon loading is
controlled by a parse file. A schematic view of the parse file is shown in
Figure 38.
Figure 38: Schematic view of the parse file for image description settings.
Correctly defined image description parameters is important in the use of
automatic analysis tools. The image description is divided into three parameters; Imaging technique, Image type and Image view plane. The definition
of image description parameters is controlled by manually change the parse
file imagedescption.tex according to Figure 38. This make it possible to adjust the definition of image description parameters to different acquisition
parameters settings. There are no limitations in the number of specifications
below each image description parameter. An example of a parse file is shown
in Figure 39. If you have questions, please contact support@medviso.com
for further details.
23.2
Advanced and DICOM Settings
The graphical interface for advanced settings is shown in Figure 40. The
GUI is divided into four sections; Database settings; Segment Server settings; Sending DICOM files; and DICOM interpretation.
87
CHAPTER 23. CUSTOMIZATION
Figure 39: Example of a parse file for image description settings.
In this section we will only describe DICOM interpretations the other settings are explained in conjunction with Segment Server documentation, and
Patient Database Module.
The DICOM interpretation adjusts how Segment CMR interprets DICOM
files. The checkbox Force 16 bit DICOM enforces Segment CMR to assume
usage of 16 bit DICOM files, regardless what is stated in the file. This option
is helpful when images looks like chessboard when read into Segment CMR.
For further details see about loading DICOM files in Chapter 5.
23.3
PACS Settings
PACS Settings are described in the Segment Database Manual.
23.4
Technical details
On Windows platform, the preferences are stored under the local user folder
and the subdirectory Application Data/Segment CMR. This means that
each user have can set their own preferences. If you want to have it setup so
that all new users on the computer will have a default setting of preferences,
88
23.4. TECHNICAL DETAILS
Figure 40: Advanced and DICOM Settings GUI.
then copy the preferences.mat from one user to the folder where Segment
CMR is installed. Finally make this file write protected. In the preferences
folder Segment CMR also stores a log file for debugging purposes, and small
temporary files that are used in the PACS communication batchdownload
process.
89
24 Short Commands / Hot keys
This chapter describes the hot keys that can be used in the program. Note
that in many places you can also bring up a pop-up menu by using the right
mouse key to more easily access frequent menu items.
24.1
Hot keys
D
S
Shift-D
Shift-S
Left arrow
Right arrow
Up arrow
Down arrow
Shift-Arrows
C
P
Shift-P
R
H
V
Ctrl-A
Shift-U
Shift-A
Shift-1
Shift-2
Alt-2
Shift-3
Alt-3
Shift-4
Shift-6
Alt-6
Shift-9
Go to end diastole
Go to end systole
Go to end diastole in all visible image stacks
Go to end systole in all visible image stacks
Previous time frame
Next time frame
Next slice in basal direction
Previous slice in basal direction
Same ass Arrows but applies to all visble image stacks
Start to play cine thumbnail
Start to play movie
Start to play movie of all visible image stacks
Refresh screen
Hide/show all contours and markers
Shift mode in panel between montage and one slice
Selects all slices
Unselect all slices
View all image stacks
View one image panel
View two image panels
View two image panels as rows
View three image panels
View three image panels as rows
View three image panels
View six image panels
View six image panels as rows
View nine image panels
91
CHAPTER 24. SHORT COMMANDS / HOT KEYS
Ctrl-1
Ctrl-2
Ctrl-3
Ctrl-4
Ctrl-5
Ctrl-L
Ctrl-M
Ctrl-Shift-M
Ctrl-Alt-M
Ctrl-R
Ctrl-Shift-R
Ctrl-Alt-R
Alt-R
Ctrl-F
Ctrl-Shift-F
Ctrl-Alt-F
Alt-F
Ctrl-T
Alt-T
Ctrl-U
Ctrl-Shift-U
Ctrl-Alt-U
Ctrl-D
Ctrl-Shift-D
Ctrl-Alt-D
Ctrl-V
Space
Shift-L
Shift-R
Shift-F
Shift-V
Shift-M
Shift-I
Ctrl-B
Ctrl-N
Ctrl-O
Ctrl-P
Ctrl-Shift-G
92
One view
M-mode view
Montage view
Montage row view
Montage fit view
Perform fully automatic LV segmentation
Segment LV endocardium
Segment LV epicardium
Segment RV endocardium
Refine LV endocardium
Refine LV epicardium
Refine RV endocardium
Refine Flow ROI
Propagate LV endocardium (epi if next timeframe already has en
Propagate LV endo and epicardium forward and refine
Propagata RV endocardium forward, do not refine
Propagate Flow ROI forward and refine
Track tool for LV endocardium
Track tool for Flow ROI
Copy LV endocardium upwards and refine
Copy LV epicardium upwards and refine
Copy RV endocardium upwards and refine
Copy LV endocardium downwards and refine
Copy LV epicardium downwards and refine
Copy RV endocardium downwards and refine
Exclude papillary muscle from LV enocardium
Toggle tool in toolbar menu (depending on tool and mode).
Select LV mode
Select RV mode
Select ROI/Flow mode
Select Scar(Viability) mode
Select MaR mode
Select Misc mode
Bullseye plot
Load next .mat file
Load image stack
Open patient data base
24.1. HOT KEYS
¿ Reset GUI Position
Ctrl-S
Ctrl-W
Shift-Ctrl-W
Ctrl-Q
Ctrl-Z
Ctrl-plus
Ctrl-minus
Mouse wheel
Shift-Mouse wheel
Ctrl-Mouse wheel
Alt-Mouse wheel
Save all image stacks
Close current image stack
Close all image stacks
Quit program
Undo segmentation
Zoom in
Zoom out
Scroll through slices
Scroll through time frames
Scroll through visible thumbnails
Zoom
93
25 Support
25.1
Submit bug report
When submitting a bug report it is very important to describe how to reproduce the bug and to provide the log file for the session. In many cases it is
also necessary to provide some files that can be used to analyse the problem.
It may either be .mat files or DICOM files when the problem is loading data
into Segment.
To submit a bug report, select the function Support Request under the Help
- Support menu. This will open the graphical user interface where you can
describe the bug and attach log files and data such as .mat files or DICOM
files. When all information is entered you press the Send support request and
the description entered and the attached files are submitted to Medviso.
By changing the type you can also submit general questions or enhancement
requests.
Hints to remember:
1. Even though the submitted files are encrypted your files should be
anonymized. Anonymization of .mat files are available under either
Image Tools menu or the Utilities menu. Anonymization of DICOM
files are available under the Utilities menu.
2. Additional files to submit should be placed in a folder and the folder
is then submitted.
3. Remember to name your files wisely, otherwise we will not be able to
identify which file belongs to which support request.
4. Remember to mention the filename uploaded in your support question/request.
95
CHAPTER 25. SUPPORT
25.2
Data privacy policy
Medviso AB will strictly keep the data safe and not distribute it and any
data or information from it (such as possible pulse-programming ideas, postprocessing ideas, etc etc). Medviso will not utilize it for other purposes
than debugging purposes or to answer the specific questions unless other is
agreed upon. When the support case has been closed, then the data will
be deleted. If you have questions, please contact support@medviso.com for
further details.
25.3
General support issues
To get into contact with developers at Medviso AB, send email to
support@medviso.com.
96
26 Implementation Details
In this chapter a few implementation details are given. There are much more
details that are interesting, but this is as far as we have got with the documentation. If you have specific questions, please do not hesitate to ask us.
26.1
Numeric representations
All numbers are stored and used internally as double precision floating points
with the following exceptions:
• Images are stored as single floats (normalized) or as integers (uint8),
and then as they are stored in the DICOM files. Most functions in
Segment will automatically convert the data to floats.
• Edge detection results are stored as integers (16 bits, ’normalized’)
• Character strings are stored in 8bit ASCII format
• Infarct maps are stored as int8 (manual interaction), and uint8 (result).
• General segmentation tool store objects as levelset function with an
uint8 representation where the zero levelset resides at 128.
Internally the image stack is normalized upon loading by a global maximum
intensity such that all values are [0..1]. Offset and scaling is also calculated
so that the image stack can be reconverted back to original signal intensities.
26.2
Loading data and interpretation of DICOM tags
This section describes how Segment interprets DICOM information to calculate important parameters suchs as geometric properties of the images.
• Number of slices. This is calculated from the presence of different slices
based on the DICOM tags ImagePosition and ImageOrientation.
• Number of timeframes. This is based on dividing the total number of
images with the number of slices.
97
CHAPTER 26. IMPLEMENTATION DETAILS
• Time increment in ms between each timeframe. If uniform, this is
based on the difference between the number of timeframes divided by
largest and the smallest value of the DICOM tag TriggerTime. If the
DICOM tag TriggerTime is not present then the DICOM tag TR is
used as time increment. Note that this might depent on your k-space
acquisition scheme so for scanners that do not report TriggerTime you
really need to double check the estimated value of time increment. For
perfusion and other image stacks with non-uniform time increment,
this is calculated using differences in AcquisitionTime.
• Heart rate. The heart rate is taken from the DICOM tag HeartRate if
present. Note that many vendors (including Siemens) does not specify
this. As a fall back Segment tries to calculate the heart rate assuming full R-R intervall coverage by using of trigger time (i.e it does not
working for prospective imaging series). For long image acquisitions
where one image is taken approximately for each heart beat then the
heart rate is taken as the time between start of image acquisition and
end of image acquisition adjusted for the number of frames. Note that
in many cases this heart rate calculation will fail. Heart rate can be
adjusted under patient details. Note also that heart rate may vary between image stacks therefore do not press Apply for all when manually
changing heart rate. Heart rate is not used in any calculaion, instead
time increment between image frames is used in all calculations.
• Slice thickness in mm. The slice thickness is taken from the DICOM
tag SliceThickness. If this tag is not present then the information is
taken from same DICOM tags as number of slices, and assuming slice
gap to be 0.
• Gap between slices in mm. This is taken from the DICOM tag Spacing
BetweenSlices.
• Pixelspacing in X-direction in mm (vertical direction in Segment). This
is taken from the DICOM tag PixelSpacing.
• Pixelspacing in X-direction in mm (horisontal direction in Segment).
This is taken from the DICOM tag PixelSpacing.
• Velocity encoding (VENC) in cm/s. For non velocity encoded images
this should be 0. How this is interpretated involvs proprietry information of different scanner vender information.
98
26.3. VOLUME CALCULATIONS
• Rotated image stack. This should by default be false. If your image
stack is rotated, then change this to true. Currently this parameter is
not taken from information in the DICOM tags and the user needs to
manually change this when loading rotated image stacks.
• Cyclic image. If the image stack is cyclic, i.e covers the whole heart
cycle this should be true (default). For prospectively gated image series
this should be false. This affects mainly the automated segmentatin
algorithm. Currently this information is not read from the DICOM
information.
26.3
Volume calculations
The volume calculations are done by a summing the area in each slice. The
main reason for not using a more advanced volume integration method is
that no one else is using that and therefore it might be difficult to compare
the results. Segmentation (i.e. delineation of endocardium and epicardium)
is stored on a sub-pixel accuracy and subsequent calculations are on a subpixel basis. For viability the classification into viable or scar is done on a
pixel-wise basis and there the volume calculations are done by summing the
number of pixels.
For the rotated image stacks the volume is given by a integration method.
The volume contribution of each outline is given by :
Z
dy
π
(1)
y(s)2 sign(y(s)) ds
δV =
2∗Z
ds
where the curve is given on a parametric representation (x(s), y(s)), Z is the
number of slices in the rotated image stack. No long-axis compensation is
performed for the rotated image stacks.
26.4
Mass calculations
When converting volume to mass the density is assumed to be 1.05 g/ml.
Note that this number differs in the literature between 1.04 to 1.05. Furthermore, note that these numbers are valid for healthy myocardium ex-vivo,
what happens in for instance infarcted regions is not shown in the literature.
Therefore usually it is better to report volume instead of mass.
99
26.5
Calculation of BSA
The formula used is based on Mosteller.
r
BSA =
w∗h
3600
(2)
where w is the body weight in kg, and h is height in cm.
26.6
Peak ejection/filling rate
When calculating peak ejection and peak filling rate the volume curve is
differentiated using forward difference approximation. For cyclic datasets
cyclic convolution is used for the calculation.
26.7
Wall thickness
Currently wall thickness is defined as the thickness along a radial spike from
the endocardial or the epicardial center (depending on setting in the preferences. In the future I plan to also include the modified center line method.
Note that the centers are calculated for each timeframe separately.
Wall thickening is defined as the wall thickness in end-systole minus the wall
thickness in end-diastole. Note that it is possible to manually or automatically select what timeframes that are diastole or systole respectively.
Fractional wall thickening is defined as:
W Tf =
W T − W TED
W TED
(3)
Where W Tf is fractional wall thickness and W T is wall thickness and W TED
is wall thickness in end-diastole. In the bulls eye plot then fractional wall
thickening is showed in end-systole.
100
26.8. CALCULATION OF REGURGITANT VOLUMES AND SHUNTS
26.8
Calculation of regurgitant volumes and shunts
The regurgitant fraction for the aortic valve and the pulmonary values are
calculated as:
r = 100
vback
vf orward
(4)
where r is regurgitant fraction, vback is backward volume, and vf orwd is forward volumes. Backward volumes is taken as timeframes where the net flow
is negative and integrated over the entire cardiac cycle.
The regurgitant fraction for the tricuspid and mitral valve are calculated as:
r = 100
SV − vf orwd
SV
(5)
where r is regurgitant fraction, and SV is stroke volume for left or right
ventricle, respectively. vf orwd is forward volume.
The Qp /Qs ratio is defined as
Qp Qs =
Qp
Qp
(6)
where Qp is the stroke volume of the pulmonary artery and Qs is the stroke
volume of the aortic artery.
26.9
Infarct size, extent and transmurality
Calculations of infarct sizes etc are based on ’counting’ pixels, i.e. each
pixel has a binary classification. There are two methods for regional analysis
available, one are based where the percentage of the pixels that are inside the
sector. The other method is based on radial spikes from the center (endoor epicardial depending on setting in the preferences). The line between endocardium and epicardium is resampled in 50 steps and the percentage of
infarcted pixels are counted.
101
Infarct extent is defined as the projected infarcted area on the endocardial
surface [?].
Iext =
X Ti Ri
i
Ri
(7)
where Iext is the infarct extent, Ti is the transmurality of sector i and Ri is
the mean endocardial radius of sector i.
26.10
T2/T2* calculation implementation
The signal intensity S in the images can be described with an exponential
fit according to:
S = K ∗ e(−R2 ·TE )
(8)
where R2 is 1/T2 , and K is an arbitrary constant. In order to calculate
the exponential fit one need at least three echo times (in theory two would
be enough, but to ensure numerical stability Segment requires at least three
points in time. The curve fitting is solved by taking the logarithm:
ln(S) = −R2 · TE + K.
(9)
where S is the signal intensity of the pixel, R2 is 1/T2 , TE is the echo
time, and K is an arbitrary constant. This equation is solved for each pixel
withing the region of interest in a least square sense by standard direct numerical method. Finally the T2 value is calculated as 1/R2 .
In the litterature, there are some evidence that a constant is advantageous
in the fitting process [?]. This constant will be implemented in later versions
of the module.
26.10.1
Calculating fitting error
The fitting error is calculated as the error of the reconstructed signal minus
the true signal value for each pixel and echo time. The error for each pixel
is calculated as the mean of the absolute value of the percentage errors for
all echo times.
102
26.10. T2/T2* CALCULATION IMPLEMENTATION
26.10.2 Smoothing
The smoothing process is done by normalized averaging, where the certainty
of each pixel is taken into acount to avoid the effect of uncertain pixels [?].
The smoothing kernel is a Gaussian smoothing kernel, illustrated in Figure 41.
Figure 41: The filter used for smoothing.
The certainty is calculated linearly as a function of the error measure calculated in Section 26.10.1. Pixels with an error with 25% or more are assigned
a certainty of zero, and pixels with zero error are assigned a certainty of one.
The cut of value of 25% is taken from [?]. Pixels where the T2/T2* value is
negative is also assigned a zero certainty. The normalized averaging is calculated by first calculating a filtered version of the T2/T2* map multiplied
with the certainty as:
M = (T · C) ∗ F
(10)
where T is the raw T2/T2* map, · is pixelwise multiplication, ∗ denotes
convolution, F is the smoothing filter kernel illustrated in Figure 41, and M
is a temporary map used to calculate the final smoothed T2/T2* value as:
T s = M / (C ∗ F )
(11)
where T s is the smoothed T2/T2* value, M is the map calculated in
Equation 10, / denotes pixel-wise division, C is the certainty map, ∗ denotes
convolution, and F is the smoothing filter kernel.
103
26.11
Longaxis volumes
Volumes can be calculated using segmentation from longaxis images. The
algorithm begins with automatically locating images labeled 2CH, 3CH and
4CH that contain segmentation. If the same kind of segmentation is found
in two such images, the volume is calculated by rotating each segmentation
area one full revolution around the axis of intersection and taking the mean of
these volumes. If there are three images that contain the same segmentation,
the volumes are calculated as described above for each pair of images, and
the mean of these three values is used.
104

Segment CMR Reference Manual

Transcription

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